In order to insert or take out loose-leaf paper sheets conveniently, a single-detent binder (also known as a loose-leaf ring binder) is widely used for a file folder or note book. As known in the prior art, a typical single-detent binder mainly comprises an elongate curved housing, a pair of elongate baseplates, a plurality of ring shaped components and one or more control handles. The two longitudinal sides of the housing are bent inwards to form two inner sides. The pair of baseplates is located inside the cavity formed by the curved housing, so that one of the two longitudinal sides of each baseplate abuts upon the inner side of the housing while the longitudinal sides on the other side of the baseplates are interconnected in parallel, thus forming a central hinge possessing a pivot axis. Each baseplate is fixedly connected to a plurality of half ring-shaped elements. At least one end of the loose-leaf binder is usually connected to a control handle, and the control handle is able to operate one pair of baseplates to move the central hinge upwards or downwards, so that the half ring shaped elements connected to the baseplates reciprocate between the open and closed positions.
In said single-detent binder mechanism, a user operates the handle on the control component to occlude and disjoin the rings. The handle procures the opening or closing by moving a pull rod (also known as a travel bar in some prior arts) connected to it which eventually procures the opening or closing of the rings, which move the central hinge upwards or downwards through its extension arms. In general, such handle is made of plastic and pivoted on a pivot pin for rotation. When the binder is operated repeatedly, the plastic handle is under constant and repeated exertion of force by the user which can cause material weakening, fatigue and deformation. In some cases, the extension arms on such handle can even be bended and cracked when excessive force is applied to the handle by the user. As the handle forms an essential and irreplaceable part of the whole mechanism, without the handle, the whole single-detent binder will be useless. Thus, durability of the handle and other internal components upon repeated operation of opening and closing of the ring is a vital feature of the control component for prolonging the life of the single-detent binder.
United States Pub. App. No. 20150063896 discloses a ring binder mechanism in which the control handle (referred to as actuator in the application) causes the pivoting motion of the hinge plates through its closing arm against the spring force from the housing to open and close the rings. However, in such mechanism, the spring force from the housing will inevitably be exerted on the closing arms and causes wear and tear and eventually breaks the closing arm, rendering the control handle useless.
U.S. Pat. No. 7,819,602 discloses a ring binder mechanism similar to the above. The control handle touches the base plate at a single pivot point. The pivot point of the handle is not directly below the lever arm on which users exert force, so that there is no support below the lever arm. Thus, excessive force exerted on the lever arm by users may thus break the lever arm over prolonged use of the control handle.
As a result, an improved design of a single-detent binder, preferably constructed with a control component that can resist excessive force on the control handle, is needed for the production of a more reliable and durable single-detent binder.